Hydraulic dynamics and photosynthetic performance facilitate rapid screening of field grown mulberry (Morus spp.) genotypes for drought tolerance

Impact of drought stress on terrestrial plants is predicted to increase in future due to rapid increase in air temperature and changes in precipitation patterns. Mulberry (Morus spp.) is an economically important perennial crop in sericulture industry. The present study was aimed at using hydraulic dynamics and photosynthetic performance for screening drought tolerance among mulberry genotypes by using non-invasive, rapid and efficient methods. Plant hydraulic variables were measured with commercially available sap flow meter, stem and leaf psychrometers in one year old mulberry genotypes. Plant leaf gas exchange parameters and chlorophyll alpha fluorescence were measured in control and stressed plants to assess their efficiency. Based on hydraulics and photosynthetic parameters, mulberry genotypes were characterized into 3 functional groups including high, average and poor performing groups (HPG, APG and LPG respectively). HPG genotypes maintained significantly better leaf water status (psi(md)), stem hydraulic conductance (K-s) and sap flow rate (F) which resulted in enhanced photosynthetic efficiency compared to APG, LPG under prolonged drought regimes as well as after recovery. Hydraulic parameters were positively correlated with photosynthetic performance of each group under drought. Our data suggest that plant water transport efficiency plays a major role in regulating photosynthetic performance which in turn determines the biomass yields under drought. Hydraulic dynamics based screening will be highly useful for rapid selection of efficient mulberry genotypes.